The invention relates to a fault current safety switch.
A fault current safety switch is known from German publication 35 37 140. Fault current safety switches are also known from German OS 4 343 560 and German OS 4 340 737. Fault current safety switches are used in electrical systems to monitor insulation, to protect against fire caused by short circuits to ground, and to protect persons against electrical shock. The term "fault current" is defined as an electrical current that flows along unintended paths as the result of an insulation failure. The value of a fault current of this kind is determined by the difference between the value of the current that flows into the system through the normal incoming and outgoing lines and the value of the current that flows out of the system. If the difference between the two currents is not zero, a fault current will flow along a path that is not the regular path. The purpose of the fault current safety switch is to separate completely the system part to be monitored from the power supply if the fault current exceeds a predetermined value. As far as the other features of a fault current safety switch according to the spaces are concerned, reference is made to the remarks in German Patent 35 37 140, where a test circuit is provided to which the secondary circuit of a total current converter is connected. The primary circuit of the total current converter is formed by the incoming and outgoing lines, so that a total current that corresponds to the difference between the currents in the incoming and outgoing lines is induced in the secondary winding. The test circuit acts on a solenoid through a switch designed as a transistor in the known fault current switch. In the prior art, the solenoid is constantly traversed by current so that it operates according to the resting current principle. When a fault current appears, current ceases to flow through the solenoid. The electromagnetic switch then assumes the open position and interrupts the circuit to be monitored. The test circuit and switch are supplied with current by a common power supply. The energy is taken directly from the circuit to be monitored.